my Spider restoration project is gathering momentum; the shell has been fully renovated (many thanks to Ben Dixey); Guy has rebuilt the original 1800cc engine ( a million thanks to GC); and I have all the parts to build the car as a rolling shell (thank you e-bay; H&N and Spider Point).

I have discussed gearbox and axle options with Guy several times over the years and opted for a 131 box with an Abarth shift and decided to fit a limited slip differential to the original axle along with a new crown wheel and pinion.

I know that several Russian made LSD's are available but I set my sights on a Colotti ( If your gonna be a bear you might as well be a grizzly!!).

After a long wait I found a perfect used one (a random search on e-bay :) and I am looking for a new crown wheel and pinion.

The car will be used on the road and any advice regarding diff ratios and where to buy a new crown wheel & pinion would be enormously helpful. Has anyone fitted Lada parts from LadaSport in Germany?

I found the car a little short legged ( pulling away in 2nd was easy) before it came off the road. The axle and diff are original as far as I can tell.

Some photos will be loaded onto this thread shortly.

Kind regards

DAVID

I have decided to try a 10/43 diff to match the 124 CSA Stradale set up.

Hadn't gotten round to answering you, sorry.
The 131 box is fine considering durability and shifting (at least that's what people tell me), so if you can get one and can modify the tunnel before all sheetwork and spraying is done: by all means do it. As far as I know the front half of the drive shaft thate was fitted to auto'boxes (US spec) would be a good match to the longer tail of the 131 box. Or get a bespoke shaft made (shortened).
Regarding ratios there is only one real difference: the Spider had a shortish 5th (0,88 over 1.00 in 4th), while in the 131 that was more like 0,83 and that suits bigger engines and fast cruising rather than twisty B-roads and the occasional highway. A more modern top gear. It will lower revs in 5th by some 200-250 revs/min which is nice but not too spectacular.

If the CSA Stradale just had the standard Spider diff ratio (couldn't find the documentation on that), I guess that was off the shelf so both simple and cheap for Fiat to do and it suited the intended sporty / rally use. Competition cars would run much shorter diffs.

You're going to drive on the roads, so maybe you'd like somewhat taller gearing.
Considering your engine upgrades I feel you could do with both the taller 5th from the 131 box and also a 4.1 diff. That way you will get slightly longer 1-4th gears compared to original and a nice relaxed 5th for cruising which still isn't too long. The engine will certainly be able to cope with that.

I do not have personal experience (yet) with the Russian LSD's (Quaife ATB clones by the looks of them) but I'm certainly very interested in hearing about those. Some of our nordic friends will be able to tell us more. You can also find them under 'links'. viewtopic.php?f=11&t=3207

I have a Colotti T90 LSD and have been advised that a standard Fiat (or Lada) crown-wheel & pinion will bolt straight onto it. The transmission tunnel will be modified by a highly skilled sheet metal worker locally once the engine and box is offered up to size the adjustments. I have found some informative articles and photos on the net that offer some background information. There are some horror shows out there as well where sledge hammers and baulk timbers have been used to beat the inappropriate out of the tunnel !!!.

The 131 box that I have is a standard 5 speed with the Abarth quick shift. This will be rebuilt by the same engineer who will re-build the axle and fit the LSD. I like the sound of a slightly taller gearing so the 131 box should work well with the suggested 4.1 diff. I can get the existing shaft shortened locally as well.

I do have a lot of photos that show the body shell restoration and I will upload a selection over the weekend.

The project will gather a good head of steam in the autumn when my older brother completes the build of his workshop. Happy days :)

I have a 1971 124 Spider with a mildly tuned 2 liter engine. I fitted a Lada 43/11 (3.9:1) ring and pinion almost 10 years ago and I like the more relaxed cruising it provides. The car also has a 0.80:1 5th gear from a Polski (not all had this ratio), which further reduces the revs on the highway.

It all depends on what kind of driving you will do. Here I usually drive 3-4 hours to club meets, so a quieter car is important. If you will mostly drive back roads and rarely go over 70mph, then you could stay with the stock 4.3 ratio and see how you like it.

I've seen Lada ring and pinion gear sets where the machining was not entirely finished and the correct mesh was impossible to set up. Upon closer inspection one could see from the finish on the gear teeth that something was not right, so this should be easy to spot if one is looking for it.
We actually carry the 43/11 ring and pinion, as well as the complete third member, as it is a popular swap here in the USA.